The present invention relates to an acceleration sensor for detecting the acceleration in the horizontal direction which is suitable for movable object, such as a vehicle, and more particularly to an acceleration sensor for detecting the acceleration in the horizontal direction by detecting the movement of a ball in the lateral direction.
A retractor of a seat belt device for a vehicle is provided with an acceleration sensor for detecting the acceleration given on the vehicle. One of such acceleration sensor comprises a ball, a ball seat on which the ball is placed and which permits the ball to move in the lateral direction when the external force is applied to the ball in the lateral direction, and a detecting means for detecting the movement of the ball from the ball seat.
U.S. Pat. No. 3,927,286 discloses an acceleration sensor in which a concentric conductive detection ring is disposed around a concentric conductive ball seat ring. The conductive ball moves from the ball seat ring due to the external force applied in the horizontal direction and comes in contact with the detection ring so that the rings are conducted through the ball, thereby outputting an acceleration detection signal.
British Patent No. 1,531,973 discloses an acceleration sensor in which a ball is placed on a ball seat whereby a micro switch is pushed. As the ball is moved, the pushing force exerted on the micro switch is released so that a signal is outputted from the micro switch.
Japanese Unexamined Patent Publication No. 64-54362 (the convention priority was claimed based on West German Patent Application No. 3725758.7) discloses an acceleration sensor comprising a light emitter disposed on either one of upper or lower sides of an inertia member having a spherical bottom and a light receiver disposed on the other side of the inertia member which is provided with a through hole in the optical axial direction for communication between the light emitter and the light receiver. As the inertia member tilts due to an acceleration in the lateral direction, the through hole deviates from the optical axis so that the optical communication between the light emitter and the light receiver is blocked, thereby outputting a signal.